Make one, I did that before with the powerpoint color scheme mixing, but how can you do it in paint or photoshop??

What I actually did yesterday is take an MRI of an intracranial aneurysm from the web, which is grayscale, change the color balance so that it became blue and wash it out which makes a nice background. The only problem is I guess, that I probably am not allowed to use that in a big meeting since it is not my image. Right?